Why is there sand in deserts and no dirt? Why isn’t there sand anywhere else?

Question

I figured it was something to do with sand being light enough to be carried by wind, but that wouldn’t explain why the rest of the world lacks sand.

In: 327

Answer 1

Because “dirt” aka “soil” is composed of both inorganic material (like the silica in sand) and decomposed organic material (carbon, nitrogen, etc).

In order to build soil, you need adequate moisture and nutrients for plants to grow, die (or drop leaves), and be broken down by decomposers (insects, bacteria, and fungi), and you need some kind of root structure or a layer of humus to hold the soil in place and prevent its being eroded away by wind and water.

You don’t have those things in a desert. Not enough water for significant plant growth, not enough organic nutrients in a purely mineral sand, and nothing to prevent the desert wind from blowing away any soil that does form.